To help you tell whether my evaluation is worth reading, these are the (music capable/usable) devices I own/owned and use/used actively:

iPod Touch (first gen)

iPad 1

Zune Player

T-Mobile G1

Google Nexus One

Galaxy Tab 7’’

Galaxy Tab 10.1

Windows 7 HTPC

And these are online music services I’ve used (either currently -soon to be dropped- or very recently). Note that they offer varying services and capabilities, so they cannot be compared easily, but they are all related to music, and I’m just noting the plus/minus I found for each:

iTunes – No streaming - Sync with a freakin’ cable, etc. - Pay per song/album - Epic #fail. (The first two alone discouraged me enough that I never bought a single song through it. Yeah, there’s a beta 10.4 of “iTunes in the Cloud” now, which still doesn’t do streaming. Too little, way too late)

Google Music: haven’t used it yet, but looks to be more or less like Amazon’s (-recommendations)

Last.fm subscription: $3 per month + Multiple devices supported (even XBox!) - No offline support - No custom playlists that I could find

So I set out to try out for a month Spotify. Got a Premium account, and downloaded the desktop, Android and iPod clients. I hate iTunes with a passion, so I would have preferred a more creative desktop client than essentially a cleaned-up version of iTunes. I wish they copied Zune software instead which is truly gorgeous and (r?)evolutionary as a media player.

Now, here’s how you do sync in this age, Apple:

At no point, ever, you need to connect a cable between your computer and your device. Ever. Here I’m sync’ing for offline play on the laptop the most excelent Nightwish End of an Era CDs right off the cloud (I don’t own this album).

Here’s another view but now sync’ing to my Nexus One phone:

And now with ALL my current devices (except for the Zune) connected (couldn’t rename the Galaxy Tab 10.1 device, option appears greyed out ):

Truly amazing. Totally sold.

Needless to say, you can of course do everything you can do from the desktop client (except manage sync on other devices, AFAICS) from each mobile client (search, create playlists, cache for offline, etc.).

One thing I didn’t like is that you can only play on one device at a time. Starting on another pauses whichever other device is using the same username. I prefer the Zune’s approach of letting up to 5 simultaneous devices to be used. Imagine my wife is playing something on the HTPC for my kids and at the same time I’m working on my office. Can’t use my account on both. Means I have to pay more unnecessarily. Resorting to caching the music ahead of time and offlining one client or the other to avoid notifying Spotify and pause the other, is not going to work .

As a general purpose music player for my local files, it also looks pretty decent, so although I’m sure I’ll miss the desktop Zune software, I think I’m ready to let it go.